Devices for applying impact forces



Nov. 9, 1965 H. BRIDEN DEVICES FOR APPLYING IMPACT FORCES 3 Sheets-Sheet 1 Filed Aug. 20, 1962 0Q 02 :1 Os vn mv 2 0 v m hi snful Ow N 8 O: 0: g m g @Q NE 9 2 m N Nov. 9, 1965 H. BRIDEN 3,216,510

DEVICES FOR APPLYING IMPACT FORCES Filed Aug. 20, 1962 3 Sheets-Sheet 2 In van *or I HGT-m1 fvridan Nov. 9, 1965 H. BRlDEN DEVICES FOR APPLYING IMPACT FORCES Filed Aug. 20, 1962 3 Sheets-Sheet 3 United States Patent 3,216,510 DEVICES FOR APPLYING IMPACT FORCES Horace Briden, Ashby-de-la-Zouch, England, assignor to Coal Industry (Patents) Limited, London, England, organized in accordance with the laws of Great Britain Filed Aug. 20, 1962, Ser. No. 218,056 Claims priority, application Great Britain, Aug. 28, 1961, 30,904/ 61 4 Claims. (Cl. 173-15) This invention relates to percussive mechanisms of the kind comprising a hammer and means for causing the hammer to automatically and repeatedly apply impact forces to a body. In a particular example, the present invention is intended to be mounted on a mineral mining plough and the mechanism then includes a plough cutter blade and is arranged to apply impact forces to the cutter blade during periods in which the blade is encountering resistance above a predetermined limit.

The invention is intended to provide an improved mechanism of the kind referred to, with more efficient conversion of the energy supplied into impact energy, and with improved means for absorption of the energy of moving parts.

According to the invention we provide percussive mechanism for applying impact forces to a body comprising a hammer operatively associated with two movable gas pistons between which is retained a quantity of compressed gas, the compressed gas acting, during operation, as a main spring which supplies energy to accelerate the hammer.

The invention is illustrated by way of example in the accompanying drawing, FIGURE 1 of which is a partly diagrammatic section of a mechanism in accordance with the invention with the mechanism in the position just before the release of the hammer.

In the drawings,

FIGURE 1 is a section through the mechanism,

FIGURE 2 is a diagrammatic representation of the hydraulic circuit in the condition when the mechanism is moving towards the locked position, and

FIGURE 3 is a diagrammatic representation of the hydraulic circuit in the condition when the mechanism is unlocking as the crank passes top dead centre to release the hammer.

InFIGURES 2 and 3, the convention has been adopted, for the purpose of simplification, of showing various valve operating lever systems, which are in fact physically connected to the levers 31, 37 and the roller 15, as being spaced from the levers 31, 37 and the roller 15. The dotted lines are linkages interconnecting the valve operating lever systems and the levers 31, 37, and 15. The linkages are schematically illustrated and in practice they are such that rotation of the level 201, for example, causes a corresponding rotation of lever 31 and urges the roller 32 to bear on cam surface 33 as will be here inafter described. Hydraulic pipes carrying high pressure fluid are shown in unbroken lines and. those carrying low pressure fluid are shown in long dashed lines in each of these two figures.

The illustrated mechanism comprises a mineral cutter blade 25 movably arranged in a nose casting 39 which is secured to one end of a central casting 40, these two castings 39 and 40 being in this instance adapted to be mounted on a mining machine of the plough type and accommodating a piston and hammer assembly. A release unit is attached to the other end of the central casting and is protected by a cover (not shown).

Within the central casting 40 an inert gas is held under pressure in the space 110 enclosed by a forward gas piston 123, a rear gas piston 124, and inner gas tube 119, and a liner (not shown) fitted in the bore of the central casting. The two pistons 123 and 124 are of equal diameters.

The inner gas tube 119 and forward gas piston 123 are rigidly joined together, but the rear gas piston 124 can be moved along the inner gas tube 119 to compress the enclosed gas further. Stops on the rear (left-hand) end of the inner gas tube 119 limit the maximum separation of the gas pistons 123 and 1214.

In the release unit a crank 1 which pivots about an axis. 2 is prevented from turning more than 2V2 anticlockwise past top dead centre, by means of a roller on the rod of a release jack piston 3. The piston 3 engages internal stops in a cylinder 303 at this position, and a cross-head 4 which is joined to the crank 1 by a connecting rod 5 is in consequence prevented from moving towards the right. A hammer 11 is slidable within the casting 39. The rear end of the hammer co-operates with the piston 123. The front end of the hammer has an extension tube 12 which engages with a nut 13 on the end of a rod 14 coupled at its other end to the cross head 14. The position of the linkage 4, 5, 13, 14 and crank 1 (shown in FIGURE 1) is herein referred to as the locked position.

A main piston 6 is moved to-and-fro by fluid pressure obtained from hydraulic circuits to be described, in chambers 43 and 44 acting on its two annuli 7 and 8. The smaller annulus 7 is subject at all times to high fluid pressure While the larger annulus 8 is subject to the pressure of fluid in the chamber 44 which is connected either to pressure or to exhaust by a main control valve 240 included in the hydraulic circuits shown in FIGURES 2 and 3.

With the crank 1 abutting the jack piston 3 and thus in its locked position, high pressure fluid from a source to be mentioned hereinafter is fed to the chamber 44 to act on the larger annulus 8 and the main piston 6 moves towards the right taking the rear gas piston 124 with it. The gas loads acting on the tWo gas pistons 123 and 124 are now no longer self balancing as they were when the piston 124 was tight against the stop at the left-hand end of the inner gas tube 119, and the gas pressure acting on the rear face of the forward gas piston 123 is pressed against the hammer 11 with an increased pressure. The latter is restrained from moving by its extension tube 12 which engages with the nut 13 at the forward end of the linkage tie rod 14, this rod, being joined at its other end to the cross-head 4, is held locked against movement to the right by the crank 1.

A roller 15, see also FIGURES 2 and 3, carried on a resiliently loaded lever 18 pivoted to the centre casting bears on the left-hand end of the main piston 6. The roller 15 detects any movement of the main piston 6 since if the latter moves to the right the resilient loading of the lever keeps the roller in contact with the piston. Hence the compression of the gas can be detected and when this compression reaches a predetermined amount, for example when the main piston has moved 1.75 inches, the lever 18 (as can be seen from FIGURES 2 and 3) acts through a further lever system including a bell crank lever 208 to cause the spool of a valve 210 to move to the left as is shown in FIGURE 3. This allows oil from the release valve 210 to pass to the release jack cylinder 303 via an auxiliary cylinder 202 (see FIG- URE 3) and when high pressure oil is supplied to the cylinder 202 the piston 203 of the auxiliary cylinder is moved just prior to that of the release jack piston 3, and acting through the auxiliary linkage 204, 201, lifts the roller 32 carried by the lever 31 clear of the crank 1 into the position shown in FIGURES 1 and 3 before the piston 3 starts to move. The high pressure oil applied to the release jack cylinder 303 is now able to move the piston 3 to the left. Further compression of the gas while the release jack piston 3 is extending is limited by the tail shaft 129 of the hammer 11 which engages with the main piston 6 through a conical thrust member 130 and a cushioning piston 126. The cushioning piston 126 is slidable within a cylinder 134 formed within the main piston 6. The cylinder 134 communicates with the chamber 43 through parts 142 (only one being shown). A flap valve 137 co-operates with the parts 142, the valve has small calibrated apertures which provide controlled. leakage paths. In the drawing these are conveniently represented by a space between the adjacent hatching lines. In this way relatively free flow past the value is possible in one direction, but only a restricted flow is possible in the opposite direction. The piston 126 is able to exert a force upon the rear piston 124, through a conical thrust member 130, the shaping of the thrust member being such as to accommodate the differences in diameters of the piston 126 and an annular abutment on the rear piston 124 and to provide different thrust areas at its opposite ends. When the release jack piston 3 moves far enough to push the crank 1 past its top dead centre it unlocks the linkage and leaves the cross-head 4 free to move the right.

The gas at its increased pressure acts on the forward gas piston 123 and accelerates it to the right taking the hammer 11, the linkage tie rod 14, nut 13, cross head 4 and connecting rod 5 with it, the crank 1 being rotated in a clockwise direction. After moving a predetermined distance, for example 1.50 inches, the hammer 11 impacts on the end of the blade tail shaft at 17.

As the crank 1 is rotated by the jack piston 3 a valve cam 20 which is integral with it moves a cam follower 21 which is arranged to act through a linkage system 221, 222 to reverse the setting of a pilot valve 220 associated with a main control valve 240 thereby moving the piston valve 220 from the position shown in FIGURE 3 to the position shown in FIGURE 2. The main control valve 240 controls the admission of pressure fluid from the chamher 261 to the chamber 44 and from the latter to exhaust, thereby controlling the pressurisation of the piston 6. This reversal of the pilot valve 220 setting causes the main control valve 240 to connect the chamber 44 to exhaust line through an annular distribution chamber 262. An over-center device (parts 223-6) and an arrestor device (not shown), which latter forms not of the present invention andtherefore is not discribed, arrest and hold the pivlot valve 220 and its operating lever system 221 and 222 in this position. The over-centre device, shown diagrammatically, comprises a lever 225 pivoted at 226 carrying a latching surface schematically indicated at 223 which is adapted to be engaged by the end of lever 221 when the latter has been moved into the position shown in FIGURE 3, that is from one side to the other of the vertical plane passing through a predetermined position on the lever 221. A spring 224 resiliently urges the lever 225 towards the lever 221.

After impact the cross-head 4, linkage tie rod 14 and nut 13 continue moving towards the right, taking the connecting rod 5 and crank 1 with them until a shoulder 140 on the cross-head 4 engages with stops 141 on a cushioning piston 126. This cushioning piston 126 in turn moves towards the right, discharging oil from a cushioning cylinder 134 into the chamber 43 through ports 142 in the main piston 6, and past a flap valve 137 which lifted off its seat and does not restrict this flow. From the chamber 43 the oil can flow back into the main pressure circuit through the valve 240.

The movement of the cushioning piston 126 towards the right against the hydraulic forces exerted on it absorbs the energy of the moving linkage 1, 4, 5, 13, 14 and brings it to rest, meanwhile the same hydraulic forces tend to move the main piston 6 towards the right. These forces are less than the sum of the hydraulic forces acting on the annulus 7 and the gas loads acting through the rear gas piston 124 on to the main piston 6, and the latter starts moving towards the left. The axial length of the conical thrust member is such that the cushioning cylinder can complete its cushioning stroke before it contacts the member 130.

When the cushioning piston 126 and the linkage have the same velocity as the main piston 6 the high pressure oil from the chamber 43 starts to flow back into the cushioning cylinder 134. The flap valve 137 closes and the restricting orifices in the valve 137 restrict the rate of this oil flow so that the cushioning piston 126 andmain cylinder 6 re-engage gently and the linkage 1, 4, 5, 14, 14 moves only slowly towards the left.

Should the coal or other body to which impact is applied absorb only p artof the energy of the blow, the movement of the blade 25 towards the right is restrained by a collar 28 on the nut 13 engaging with the blade 25, the same nut 13 applying a similar restraint to the hammer 11 through the extension tube 12. The inertia of the hammer 11 and blade 25 continues to accelerate the linkage 1, 4, 5, 13, 14 towards the right, thereby tending to impose undue forces upon the crank 1 and the connecting rod 5. This is avoided by arranging that the physical properties and dimensions of the linkage tie rod 14 and hammer extension tube 12 are able to provide the necessary resilience at re-engagement of the hammer extension tube 12 with the collar 28 to protect the bearings of the crank 1 and connecting rod 5 against damage. As soon as this re-engagement takes place the cushioning piston 126 again provides the initial retardation as described above until the axial clearance of the conical thrust member 130 is taken up and piston 126 moves the member 130 to contact the rear gas piston 124 is moved towards the right away from the main piston 6.

The net hydraulic force acting on the main piston 6 is now towards the right, the area of the annulus presented in the cushioning cylinder 134 being larger than the effective area of the annulus 7, and the main piston is accelerated towards the right. During this accelerating period oil flows freely out of the cushioning cylinder 134 past the flap valve 137, but as soon as the velocities of the main piston 6 and the other masses are equal, the flap valve 137 closes as flow reverses and is then restricted and the main piston 6 and the rear gas piston 124 reengage at a low relative speed.

All the moving parts are thus brought to rest, their energy being absorbed by the work done against the high pressure oil in the chamber 43 and cylinder 134, by drawing oil from exhaust at high velocity through the main control valve 240 and the interconnecting ports into the chamber 44, and against the gas load exerted on the rear gas piston 124, the forward gas piston 123 being held meanwhile by fixed stops 27 in the casting 40. The main piston 6 is now moved towards the left by the gas loads acting on the rear gas piston 124 and hydraulic forces acting on the annulus 7, but the movement is heavily damped by the flow of oil out of the chamber 44. When the main piston 6 reaches the position where release occurs, i.e. that shown in FIGURES 1 and 3, the rear gas piston 124 engages the stops on the inner gas tube 119 and now only the hydraulic forces move the main piston 6.

From this position the cation is the same whether or not the blade has been fully arrested by its impact. The.

cylinder and piston 36 and 35 and these of the annulus 7 are chosen so that the piston rod 35 can exert a greater force on the blade 25 acting towards the right than the O1]. acting on annulus 7 can exert towards the left, consequently the impact cycle stops until the coal loading on the blade 25 exerts sufiicient axial thrust to overcome this net force acting on the blade 25 towards the right.

The motion of the main piston 6 towards the left is detected by the roller 15, and the setting of the release valve 210 is reversed by means of the lever system 18, and 208 causing the release jack piston 3 to move the right as shown in FIGURE 2. The setting of the release valve 210 also causes the auxiliary cylinder 202 to act through its linkage 201, 204 to bring the roller 32 on the lever 31 to bear on a second cam 33 integral with the crank 1. As the crank 1 approaches its T.D.C. the turning moment exerted on it by the thrust of the connecting rod 5 decreases, but the shape of the cam 33 is such that the roller 32 exerts an increasing moment which drives the crank 1 over T.D.C. into contact with the release jack 3 and holds it there against any tendency to bounce back.

As the crank 1 locks in the position shown the hammer 11 is cushioned by the gas in the space 110, and the main piston 6 is cushioned by the cushioning cylinder 134, the cushioning piston 126 moving to discharge oil which absorbs the energy of these moving masses. The linkage mechanism 1, 4, 5, 13, 14 is again protected against the shock of re-engagernent of the rebounding hammer 11 with the collar 28 (rebounding ofi the compressed gas between the gas pistons 123 and 124) by the resilience of the linkage tie rod 14 and hammer extension tube 12.

As the crank 1 moves anti-clockwise, a peg 38 engages with the lever 37 which operates the pilot valve 220, this being set to move immediately after the crank has passed its T.D.C. position moving anticlockwise the main control valve 240 to the position shown in FIGURE 3 in which high pressure oil is fed to the chamber 44. The cycle now continues as from the point at which high pressure oil is fed to the chamber 44 with the crank 1 locked, as hereinbefore described.

The roller 15 is resiliently loaded by a loading cylinder 250, with a piston rod 251, is continuously fed with high pressure oil and acts, through linkage 252 and 253, to continuously urge the roller 15 into contact with the main piston 6 except during the period in which the piston 6 moves in consequence of the blade not being arrested by impact. This ensures that movements of the piston 6 are detected as aforesaid. The annular chambers 261 and 262 are distribution chambers for the high pressure oil and low pressure o-il respectively, and are connected as indicated to a high pressure supply and to exhaust.

The pilot valve 220 and the main control valve 240 may be fabricated in a single valve block, schematically represented by chain-dotted lines in FIGURES 2 and 3. The valve 210 and cylinder 250 may be similarly arranged.

In the arrangement of a percussive mechanism according to the invention on the body of a mineral mining plough one of whose blades is then constituted by the blade 25, when this blade encounters resistance above a predetermined limit an impact of more than 2 inch-tons (and preferably approximately 12 inch-tons) is applied to the plough blade to break down resistant mineral. The frequency of such application is preferably less than 180 per minute and advantageously about per minute. The ratio of the mass of the hammer to that of the cutter blade is preferably greater than 2:1 and may for example be 2 /2:l. A percussive plough as described in this paragraph has been found to have many advantages over prior known percussive ploughs, which differed from the present plough in giving only very much lighter impacts at a much higher frequency.

I claim:

1. A percussive mechanism for applying impact forces to a body, comprising a housing, a hammer disposed in said housing for movement in a predetermined direction to apply an impact force, means for locking the hammer against movement in said direction, a cylinder in said housing, a first piston slidably disposed in the cylinder and adapted to move said hammer in said direction, a second piston slidably disposed in said cylinder and spaced from said first piston to define a gas space therebetween for a quantity of a gas, means adapted to displace the second piston toward said first piston to reduce said gas space and pressurize any gas in said space to increase its stored energy, and release means connected to operate said locking means to allow the gas to expand to drive said first piston and the hammer in said direction.

2. The percussion mechanism of claim 1 and including means responsive to resistance to movement of said body, for actuating said release means to operate said locking means to release said hammer, thereby permitting the first piston to urge the hammer in said direction.

3. The mechanism of claim 1, including a third piston for displacing said second piston, said third piston being slidably disposed in said cylinder and having an initial position and a first surface thereon adapted to be acted upon by hydraulic fluid to move said third piston from said initial position to exert a displacing force on said second piston, and a second surface on said third piston adapted to be acted upon by hydraulic fluid to return said third piston to said initial position, and a cushioning chamber within said third piston, a cushioning piston slidable in said cushioning chamber, and means for coupling a linkage to the cushioning piston whereby some of the kinetic energy of said linkage can be absorbed.

4. The percussion mechanism of claim 1 wherein said locking means includes a crank arranged to latch with a linkage when at a first position relative to a top dead center position, and to disengage from said linkage when in a second position relative to said top dead center position, and a hydraulic jack operatively disposed to move said crank from said first position to said second position, and a control valve controlling said jack, and said release means includes a lever system responsive to the location of said hammer and disposed to control the setting of the control valve.

References Cited by the Examiner UNITED STATES PATENTS 964,605 7/10 Bennett 173 119 X 2,342,601 2/44 Pyle 173 119 X 2,385,439 9/45 Gubbins 173 13 2,807,021 9/57 Chellis 173 15 X 2,914,032 11/59 Powers et al. 173-39 X BROUGHTON G. DURHAM, Primary Examiner. 

1. A PERCUSSIVE MECHANISM FOR APPLYING IMPACT FORCES TO A BODY, COMPRISING A HOUSING, A HAMMER DISPOSED IN SAID HOUSING FOR MOVEMENT IN A PREDETERMINED DIRECTION TO APPLY AN IMPACT FORCE, MEANS FOR LOCKING THE HAMMER AGAINST MOVEMENT IN SAID DIRECTION, A CYLINDER IN SAID HOUSING, A FIRST PISTON SLIDABLY DISPOSED IN THE CYLINDER AND ADAPTED TO MOVE SAID HAMMER IN SAID DIRECTION, A SECOND PISTON SLIDABLY DISPOSED IN SAID CYLINDER AND SPACED FROM SAID FIRST PISTON TO DEFINE A GAS SPACE THEREBETWEEN FOR A QUANTITY OF A GAS, MEANS ADAPTED TO DISPLACE THE SECOND PISTON TOWARD SAID FIRST PISTON TO REDUCE SAID GAS SPACE AND PRESSURIZE ANY GAS IN SAID SPACE TO INCREASE ITS STORED ENERGY, AND RELEASE MEANS CONNECTED TO OPERATE SAID LOCKING MEANS TO ALLOW THE GAS TO EXPAND TO DRIVE SAID FIRST PISTON AND THE HAMMER IN SAID DIRECTION 